Antenna coupling device



Nov. 17, 1959 E. L. MINNlcH 2,913,724

ANTENNA couPLING DEVICE Filed Jan. 25, 1955 INVENTDD EDWARD L. MINNIDHBY E g TTO/PNY.'

United States Pate'nt 4O ANTENNA COUPLING DEVICE Edward L. Minnich,Carlisle, Pa., assignor, by mesne assignments, to Dynamics Corporationof America, New York, N.Y., a corporation of New York ApplicationJanuary 25, 1955, Serial No. 483,948

4 Claims. (Cl. 343-851) This invention relates to improved antennacoupling arrangements which are particularly advantageous for couplingthe output power of a transmitter to the antenna used to radiatethetransmitted signal. These coupling devices are also used to advantagefor signal reception and are well suited for transmission and receptionusing the same antenna in accordance with Well known duplexingarrangements.

With the radio communications traffic of all the allocated service bandssteadily increasing, the problem of interference between the varioustransmissions becomes more acute. As the available spectrum is fixed andthe allocation of bands `within fixed limits has been made on aquasi-permanent basis by the Federal Communications Commission, the onlyalternative which can be resorted to when additional interference cannotbe tolerated is the imposition of more stringent requirements for eachtransmission in a particular band. These limitations require thatspurious radiations from the radio equipment be reduced to a very lowlevel. In particular, in private radiotelephone service such as, forexample, the marine radio telephone band, the reduction of harmonicradiations to a greater degree than, heretofore attained is desirable.

It is the principle object of the present invention to provide in radiocommunication apparatus improved antenna coupling arrangements.

Another object is to provide antenna coupling arrangements havingextended attenuation of harmonic frequencies.

A further object is to provide improved antenna coupling arrangements-which provide convenient adjustment for obtaining optimum performanceunder all conditions of operation.

Another object is to provide the foregoing coupling arrangements whichare simple and economical in construction and completely reliable inoperation While achieving the extended performance characteristicsheretofore described.

These and other objects are obtained in the present invention byycoupling between the tuned circuit of the radio apparatus and theantenna with a spiral coil coupled to the helical coil of the tunedcircuit with an interposed Faraday shield. Spiral progressive taps onthe spiral coupling coil in combination with switch tap connection to anantenna loading coil are provided for different operating conditions.

In the drawings:

Fig. l is a partially schematic view of an antenna coupling systemshowing a side elevation of the coupled coils of the system;

Fig. 2 is a front elevation of the spiral coil and shield according tothe invention; and

Fig. 3 is a partial section View along the line 3-3 of Fig. 2.

Referring to Fig. 1 the system is shown having a conventional antenna 4for the transmission or reception or both of radio signals and isconnected to a loading coil rice 5. The loading coil 5 has connectionsat a series of taps 6 which are individually selected by a switchcontact 7 for connection with either of two leads 8 and 9. The leads Sand 9, respectively, terminate in spring clip connectors 10 and 11.

The antenna 4 transduces energy for a radio circuit 14 which hasassociated therewith a parallel resonant circuit in which the inductanceincludes a helical coil 15. The radio circuit 14 may be a transmitter, areceiver or any of the transceiver arrangements for which the antenna 4will function to transmit or receive energy as required. As an importantapplication of the present invention relates to transmitters, thesubsequent description will be made for the circuit 14 as a radiotransmitter with the coil 15 being the resonant inductance in the poweroutput circuit thereof.

The coil 15 is connected in circuit by capacitor 16 and is directlygrounded at the opposite end to a chassis terminal 17. The terminal 17may be integrally formed with a metallic chassis 18 which also serves assupport and shield for the coil 15.

Mounted to the chasses 18 is an assembly comprising separate plates 19and 20 of insulating material which may be Asecured together by anysuitable means. The plate 19 is adjacent the gorunded end of the coil15. On the face of the plate 19 which is adjacent the coil 15 issupported a Faraday shield structure 21 which preferably comprises agrid of parallel wires imbedded in the surface of plate 19 and connectedat their lower ends to a common bus 22. On the opposite face ofthefplate 19 is supported a spiral coil 23 `which may be imbedded in thesurface of plate 19 but out of contact with the shield 21. Instead ofthe spiral coil 23, a series of con, nected concentric circles may beemployed but in either case the various convolutions thereof lie in thesame plane in close proximity to the Faraday shield 21 which in turn isin close proximity to the helix coil 15.

The coil is provided with a series of taps which may be formed as loops24 projected at right angles to the plane of the coil 23. The loops 24project through appropriately spaced holes in the plate 20. One end ofthe spiral coil 23 and the common bus 22 of the shield 21' are connectedto ground at the lug 17. The spring clip connectors 10 and 11 arearranged for connection to selected ones of the projecting loops 24.

`In Fig. 2 the shield 21 and spiral coil 23 are shown as they appearbehind plates 19 and 20 of transparent insulating material. Projectingthrough the plate 20 are the loops 24 with one loop tap being providedin each turn of the spiral 23. The position of the loops or taps 24progresses for each turn with the result that adjacent loops 24 connectapproximately a single turn of the spiral wound coil 23. Behind the coil23 on the back face of the plate 19 is the shield 23 having a pluralityof parallel conductors 30 extending beyond the area covered by the coil23.

Fig. 3 shows the arrangement of the plates 19 and 20 and the preferredimbedded position for the conductor 30 of the shield 21 and the coil 23.

It is to be understood that printed circuits or etched plate techniqueslend themselves admirably to this invention. The Faraday shield 21 canin most all if not all applications be laid down on a sheet ofinsulating material with the spiral coil 23 embedded in or attached tothe opposite face. In applications where the level of power to behandled in the low spiral coil is low, printed circuitry techniques canbe similarly employed with the set of tap connections 24 riveted,soldered, 0r otherwise suitably attached thereto.

The operation of the present invention as used in a radio telephonetransmitter, for example, the marine radio band has resulted in highlysatisfactory performance together with an improvement of approximately10 db attenuation of second harmonic radiation. Operation in the upperhalf of thefband is effected with switch 7 in position to connect lead 8to one of the taps 6 on loading Ycoil 5. In similar manner operation onthe lower half of the band'obtainswith switch 7 connecting loading coiltaps 6 to lead 9. Coupling adjustments in the dilerent band switchpositions are made by means of respective clips 10 and 11.

Many variations of the disclosed embodiment will be apparent to thoseskilled in the art in the light of the present teaching and are to beconsidered Within the scope of the invention as defined in the appendedclaims. I claim: Y

1. A radio transmitting coupling system comprising a radiating antenna,a loading coil for saidV antenna having a plurality of sets of tapconnections, separate leads for connection to respective sets, switchmeans for selectively connecting said leads to said sets and providingfor each leadso `connected selective connection to the taps of therespective set, a transmitter tuned power output circuit including ahelical coil having one end grounded, said helical coil having alongitudinal axis Vand a base substantially perpendicular to said axis,a flat spiral coil having a plurality of turns with tap connections toindividual ones of said turns, means for mounting said spiral coilparallel to said base Vof said helical coil at said grounded end andcentered on said axis, a ground connection for said spiral coil, agrounded Faraday shield parallel to said spiral coil and mounted betweensaid spiral coil and said base, and means for selectively connectingsaid leads to individual'taps on said spiral coil.

2. Apparatus laccording to claim 1 in which said spiral coil is formedon one surface of a flat dielectric sheet,

said Faraday shield is formed on the other surface of said sheet, and asecond fiat dielectric sheet having holes therein is secured over saidspiral coil with said holes in registry with said taps and said tapconnections projecting through said holes.

3. A radio signal coupling system comprising an antenna, a loading coilfor said antenna, a tuned circuit having a helical coil with a at base,a at spiral coil having a plurality of turns with tap connections toindividual ones of said turns, means for mounting said spiral coilparallel to said base of said helical coil and centered on the axisthereof, a Faraday shield mounted parallel to said spiral coil andbetween said spiral coil and said base, and circuit means forselectively connecting said antenna to said tap connections.

4. In an antenna circuit for coupling to a helical coil with a flatbase, a at spiral coil having a plurality of turns with tap connectionsto individual ones of said turns, a flat dielectric plate supportingsaid spiral coil on one surface thereof, a Faraday shield mounted on theother surface of said plate, means for mounting said plate parallel tosaid base of said helical coil with said shield between said coils, andconnections to said taps for placing an antenna in circuitwith.saidspiral coil.

References Cited in the le of this patent UNITED STATES PATENrs

